Precision boring device



E. V. STATIA, SR

PREE'ISION BORING DEVICE Freb. 3, 1953 2 SHEETS-SHEET l Filed May 29, 1948 Feb. 3, 1953 E. v. sTATlA, sR 2,627,193

PRECISION BORING DEVICE Filed May 29, 1948 2 SHEETS- SHEET 2 N V EN TOR.

ATTI/s Patented Feb. 3, 1953 PRECISION BORING DEVICE Edwin V. Statia, Sr., Royal Oak, Mich., assignor of one-half to Edward L. Chapman, Detroit,

Mich.

Application May Z9, 1948, Serial No. 30,163

(Cl. 77-2l 7 Claims.

This invention relates to machine tools and, in particular, to precision boring machines.

One object of this invention is to provide a precision boring machine, wherein a boring tool is rotated and automatically fed into a roughlydrilled hole in the workpiece to bore it to a precision diameter and location, the machine being so constructed that the boring bar can be retracted from time to time and gauges inserted in order to check the progress and accuracy of the work.

Another object is to provide a precision boring machine having a supporting portion adapted to be mounted on the work and precisely located relatively to a predetermined starting point, as by the use of precision gauge blocks, the hole which is precisely bored being then used as a point of reference for the boring of another hole, and so on until the required number and location of holes has been bored.

Another object is to provide a precision boring machine wherein the feeding mechanism is so constructed that the operator may terminate the feeding action and retract the boring bar by a mere turn of the wrist in order to inspect and check from time to time the bore being made.

Another object is to provide a precision boring machine of the foregoing character wherein the radius of the cutting point or tip of the cutting tool from the axis of rotation of the boring bar may be accurately measured in a simple and direct manner.

Another object is to provide a precision boring machine of the foregoing character wherein feed gearing is provided for advancing the boring bar longitudinally at a very slow and gradual speed while it is being rotated, such as by a flexible shaft connected to a suitable source of power.

Another object is to provide a precision boring machine of the foregoing character which is portable and entirely self-contained, except for its connection to an external source of power, with the result that the machine can be moved from place to place over the workpiece in a precise manner so that the holes to be bored will be located with extreme accuracy and their dimensions will be maintained within very narrow and precise limits, the machine being thereby Well suited for the production of precision jigs, xtures, tools, dies or other devices requiring a high order of accuracy.

In the drawings:

Figure 1 is a central vertical section through a preferred form of precision boring machine according to the invention, with the various parts of the feeding mechanism shown in their driving positions;

Figure 2 is a central Vertical section through the upper portion of the machine shown in Figure 1, taken at right angles thereto along the line 2--2 therein.

Figure 3 is a horizontal section taken along the line 3 3 in Figure l;

Figure 4 is a horizontal section taken along the line 4-4 in Figure l;

Figure 5 is a horizontal section taken along the line 5-5 in Figure 2;

Figure 6 is a fragmentary left-hand side elevation of the feed disconnecting mechanism shown in vertical section in Figure 2;

Figure 7 is a left-hand side elevation of the feeding mechanism, in the upper part of Figure 1, removed from its housing;

Figure 8 is a fragmentary vertical section through the feeding mechanism shown in Figure l, but with the feeding mechanism shown in its disconnected position so that the boring bar may be manually lifted out of the hole being bored, for inspection or checking purposes;

Figure 9 is a horizontal section through the tubular support for the lower portion of the machine immediately above its enlargement. partly broken away to show the use of a micrometric measuring instrument for precisely setting the tip of the boring tool at a predetermined radius from the axis of rotation of the boring bar;

Figure 10 is a fragmentary central vertical section through the structure shown in Figure 9; and

Figure 11 is a horizontal section along the line IIII in Figure l.

Referring to the drawings in detail. Figure l shows a precision boring machine generally designated I0 as consisting generally of a tubular support I I in which a rotatable member or screw shaft I2 is rotatably mounted. The tubular support II has a tubular stem I3 terminating at its lower end in a cylindrical enlarged portion I4 having an outer cylindrical surface I5 which is precisely ground to be as nearly co-axial as possible with the cylindrical bore i6 in the stem I3. The cylindrical portion I4 is provided with elongated access openings I1 arranged at intervals around the cylindrical surface I5 for the inser- The cylindrical portion I5 is also provided with precisely ground lower and upper annular surfaces I8 and I9, the latter being surrounded by an annular relieved portion or depression 29. The surface I8 is adapted to rest upon the upper surface 2| of the workpiece W, the lower surface 22 of which rests upon a precisely finished surface 23 against which it is held by a hold-down clamp 24. The latter is approximately L-shaped with its horizontal portion 25 yoke-shaped and forced down against the surface I9 of the cylindrical portion I4 by a nut 25 threaded upon the upper portion of a stud 21, the lower portion of which is threaded into a socket 28 in the bed 29 having the precision -upper surface 23. The clamp 24 has a vertical portion 88 resting at its lower end upon the surface 23.

The bed 29 is provided with an aperture or recess 3l serving as a relief opening for a boring tool generally designated 32. The latter consists of a shaft portion or boring bar 38 having a transverse bore 34, preferably of square cross-section, near its lower end 35. The bore 34 serves to receive the shank of a tool bit 98 having a cutting tip 31. The tool bit 35 is of a cross-section adapted to nt the bore 38, such as of a square cross-section, and is held in position therein by a headless set screw 38 threaded into a bore 88 at right angles to the bore 34 (Figure 9). In order to provide a firm backing for the rearward end of the cutting tool 38, as well as to assist in the adjustment thereof, the bore 34 of square cross-section opens into a counter-bore 49 of circular cross-section. The bore 48 is threaded to receive a headless set screw 4I which, like the set screw 38, can be screwed in or out by applying a suitable wrench thereto.

The tool bit 38 when rotated by the shaft portion 33 of the boring bar 32, cuts a precision bore 45out of the side walls of a hole 45 which has been drilled in the approximate position desired for the precision bore 45. The upper portion of the boring bar 32 is provided with a tapered shank 41 adapted to fit snugly into a correspondingly tapered socket 48 in the lower end of the rotatable member I2 which is rotatably mounted in the bore I8 and which has a threaded portion 49 `immediately below the squared upper end 58 thereof, The latter is adapted to fit a chuck, coupling or socket on or in a power connection, such as a fiexible shaft connected to an electric motor (not shown). The upper end of the tapered socket 48 is provided with a threaded counterbore 5I into which the reduced diameter threaded upper end 52 of the boring bar 32 is threaded.

Immediately above the tubular stem I3, the tubular support II is provided with an eccentric hollow cup-shaped portion 53 (Figure l) having a chamber or recess 54 therein, the upper end of which is closed by a cover plate 55 held against the upper edge of the portion 53 by thumb screws 56 threaded into holes 51 therein. The cover plate 55 has an upwardly-projecting tubulaiportion 58 having a bore 59 therein co-axial with and of substantially the same diameter as the bore I6. The tubular portion 58 is provided with an annular recess 88 containing a lC-shaped spring 6I (Figure 1l) forming a resilient frictional element which snugly but yieldingly engages the threaded portion 4.9 of the screw shaft I2 so as to prevent the latter from dropping out of the machine when the feeding mechanism is disconnected in the manner described below.

The feeding mechanism unit generally -designated 62 transmits power to the screw shaft I2 by a key 83 seated in an elongated groove or keyway 64 extending lengthwise along the screwshaft I2. The recess 54 consists of a central portion B5 (Figure 4) of circular cross-section and a side portion 86 of cross-section similar to the outline of the letter U. Fitting into the recess 54 are upper and lower plates B1 and 88 respectively (Figures 4 and '7) of a feed gearing unit, generally designated 29. The plates 81 and 68 are of approximately the same outline as the recess 54 and bored to receive the reduceddiameterends of peripherally-spaced posts 59.

` The plates E1 and 88 are provided with aligned holes 'II (Figure l) adapted to receive a pin or axle 12 upon which pinions 'I3 and 14 are loosely and rotatably mounted. The pinions 13 and 14 are drivingly interconnected by a tongue and groove connection 15 (Figure 4) so as to rotate in unison. The pinions 13 and 14 mesh respectively with gears 18 and 11 co-axial with the screw shaft I2 and encircling the latter. The gear 18 is drivingly connected to the screw shaft I2 by means of the key 63 (Figure 4) whereas the gear 'I1 is free from a direct connection with the screw shaft I2.

The gears 16 and 11 and the pinions 13 and 14 preferably differ by one tooth from each other so as to provide a differential rotational effect. For example, the gears 15 and 11 may have 27 and 28 teeth respectively, whereas their corresponding pinions I3 and 14 may have 18 and 17 teeth respectively. Thus, when the gear 16 is rotated in a clockwise direction, by the clockwise rotation of the screw shaft I2 through the key B3, the gear 11 will also rotate in a clockwise direction but at a slightly slower speed. The gears 16 and 11 have hub extensions which are journaled in bores 18 and 19 respectively in the lower and upper plates 68 and 61. Interchangeable feed mechanism units 62 with different gear ratios are provided to obtain different feeding rates for the boring tool 32.

Drivingly secured to the gear 11, as by the screws 89 (Figures 2 and 3) is an annular member 8| having radial dove-tail slots 82 therein (Figure 7). Slidably mounted in the slots 82 are the dove-tail base portions 83 of nut halves 84 in the form of bars having upwardly-projecting arcuate threaded portions 85 (Figure 3) on their inner ends adapted to mesh with the threaded portions 49 of the screw shaft I 2. The nut halves 84 constitute the components of a nut device, and are slotted transversely as at 86 (Figure 3) to receive an approximately oval spring 81 which urges them outward out of engagement with the screw shaft I2. The end of the spring 81 is seated as 88 in the side wall of the cup-shaped portion The nut halves 84 are provided with partially conical outer surfaces 89 (Figure 8) forming follower portions which mate with conical surfaces 90 forming a wedging member in the cover plate 55 surrounding and leading into the bore 59. In order to move the nut halves 84 into and out of engagement with the threaded portion 49 of the screw shaft I2 by the inter-action of the conical surfaces 89 and 90, the feed mechanism unit 62 israised and lowered bodily by round-ended pins 9| (Figure 2) which at their upper ends engage the lower plate 68 and pass downward -through bores 92 in the bottom wall of the cup-shaped portion 53. The lower ends of the pins 9| rest upon the upper surfaces of cam inclines 93 (Figures 5 and 6) which are secured as by the pins 94 to a cam Vwheel or disc 95 consisting of halves 96 and 91 vsecured to one another by the screws 98 and rotatably mounted in an annular groove 99 in the tubular stem I3. The motion of the cam wheel 95 is limited by stop pins |00 and |0I (Figure 6) and provision is made for yieldably holding the wheel 95 in the position shown in Figure 6 by a ball detent |02 urged into engagement with a corresponding recess |03 by a coil spring |04 held in a bore |05 by a screw plug |06.

In order to set the top or point 31 of the tool bit 36 at the proper radius from the axis of rotation of the boring tool 32, a micrometer setting instrument generally designated |01 is provided (Figures 9 and 10). The instrument |01 consists of an arcuate rest |08 of approximately T- shaped cross-section having a cylindrical concave contact surface |09 of substantially the same radius of curvature as the precision ground surface I5 of the enlarged portion I4 on the support II so as to fit snugly together. The rest |68 is provided with a central boss I| which is bored to receive the barrel II I in which the spindle I I2 is mounted. The boss |I0 is of course counterbored for the passage of the spindle II2 and the latter is connected to the usual micrometer screw (not shown) which is threaded through the barrel III and in turn connected to a thimble II3 telescoping over the barrel III. The barrel III is provided with graduations I I4 cooperating with graduations II5 on the bevel portion II6 of the thimble I I3. The spindle I I2 has a hardened end surface I I1 for engagement with the tip 31 of the tool bit 36.

Prior to the operation of the invention, the operator adjusts the tip 31 of the tool bit or cutting tool 36 so that it is at the desired radius of curvature from the axis of rotation of the boring bar 33. This is done by subtracting the radius of the bore 45 to be bored from the known radius of the precision ground cylindrical surface I5, thereby giving the distance at which the point 31 should lie from the precision ground surface I5. Assuming that the graduations I|4 and ||5 are at zero when end ||1 of the spindle II2 lies in contact with the precision ground surface I5 (when the surface |09 of the rest |08 is snugly in contact therewith) (Figure 9), the correct position of the tip 31 of the cutting tool 36 will be determined when the operator rotates the thimble II3 in a sufiicient amount to cause the graduations I|4 and II5 to read on the same dimension as the diierence between the radii of the desired bore 45 and the precision ground surface I5, as stated above. Alternatively, the graduations |I4 and I|5 can be made direct reading on the radii of the bores 45 in a manner which is obvious from the foregoing description so that the desired radius can be set at once on the graduations.

When this is done, the end II1 of the spindle |I2 projects a distance beyond its intersection with the arcuate surface |09 equal to this difference of radii. By placing the surface |09 snugly in contact with the precision ground surface I5, and with the spindle ||2 projecting through oneof the holes I1, therefor, the end I|1 of the spindle |I2 will occupy the desired position for the tip 31 of the cutting tool 36. Thus, the operator merely has to loosen the set screv.7 38 and move the cutting tool 36 radially outward in its bore 34 until its tip 31 contacts the end II1 of the spindle I I2, which has been set as indicated above. This he may do by inserting a wrench through the opposite hole I1 into the socket in the headless set screw 4| to screw the latter in- 6. ward in its bore 40 so as to push the cutting tool 36 radially outward.

When the cutting tool 36 has been properly adjusted in this manner, the set screw 38 is tightened in its bore 39 to lock the cutting tool 36 in position, and the set screw 4I is screwed snugly up against the rearward end of the cutting tool 36 to provide a firm backing or abutment for the latter.

In the operation of the invention, after the cutting tool 36 has been set up to the desired boring radius as described above, the work W is placed upon the bed 29, holes 46 of smaller diameter having been drilled in the approximate locations for the precision holes which are to be bored. The boring machine I0 is then placed upon the upper surface 2| of the work W and the enlarged portion I4 precisely located by using the precision ground surface I8 as a surface of reference against which precision gauge blocks are placed in order to precisely locate the precision ground surface I5 relatively to whatever starting point is used for laying out the various holes 45. For work requiring less precision, in 1lieu of the gauge blocks, a circular mark of the same diameter as the precision ground surface I3 may be scribed upon the work surface 2| during the layout operations and by the use of precision layout tools. The enlarged portion I4 may then be placed within this scribed circle with the precision ground surface I8 in coincidence therewith.

Assuming that the squared portion 50 of the screw shaft I2 has been connected to the chuck or socket of a iiexible shaft or other power' source, the boring machine I0 is clamped in the foregoing position by means of the clamp 34 and the motor (not shown) started in operation in order to rotate the shaft I2. The disc 95 is then rotated -by the operator to the position shown in Figures l and 6, causing the cam inclines 93 to push the pins 9| upward and consequently to move the feed gearing unit 10 upward bodily until the conical surfaces 89 and 90 snugly engage one another. As these surfaces come into engagement, they cause the nut halves 84 to move inward so that their threaded portions 85 engage the threaded portion 49 of the screw shaft I2. Clockwise rotation is imparted to the gear 16 by the rotation of the screw shaft I2 by way of the key 63, assuming the threaded portion 49 to be a right-hand thread and the screw shaft |21 to be rotated in a, clockwise direction. This action causes the pinions 13 and 14 to rotate in a counterclockwise direction (Figure 1) causing the gear 11 to rotate in a clockwise direction at a slightly slower speed, by reason of the differential action arising from the single-tooth difference between the various pinions and gears. This has the effect of rotating the nut halves 84 in such a manner that they move the screw shaft I2 upward by a backingoif operation while it is moving downward by reason of its rotation and threaded engagement with the nut halves 84. This differential motion gives a resultant slow feeding movement downward.

When the operator desires to check the progress of the boring of the hole 45, he grasps the cam wheel and rotates it in a clockwise direction (Figure 6) causing the cam inclines 93 to move out from beneath the pins 9| permitting the feed gearing unit 10 to drop downward. This :action causes the conical surfaces 89 and 90 to separate (Figure 3), whereupon the spring 81 moves the nut halves 84 apart, disengaging the threaded portions 85 and 49 from one another enabling the'screw shaft I2 to move freely upward. The

sliding relatively to the feed gearing unit 'I0 by reason of the sliding connection between the key 63 `and keyway 64. With the lower end of the boring tool 32 raised upward out of the way, the operator then inserts his ordinary or micrometer calipers through one of the holes II and makes his measurement of the diameter of the bore 45 being bored.

To resume boring after making such a measurement, the operator pushes the screw shaft I2 downward into the boring position and again starts it in rotation. He then grasps the cam wheel 95 and rotates it in a counterclockwise direction to move the cam inclines 93 beneath the pins 9| (Figure 6) raising the feed gearing unit 'I0 bodily from the disconnected position of Figure 8 to the connected position of Figure l. rI'he inter-engagement of the conical surfaces 89 and 90 again causes a squeezing action upon the nut halves E4, causing them to move radially into threaded engagement with the threaded portion 49 of the screw shaft I2. A driving connection is thereby re-established between the nut halves 84 and the screw shaft I2 so that the gearing 16, 13, I4 and 'I'I is again rotated to cause the rotation of the nut halves 84 to resume the differential feeding motion and apply it to the screw shaft I2 as previously described.

If the operator desires to change the rate of feed, he merely unscrews the thumb screws 56, removes the cover plate 55, lifts out the feed gearing unit "I0, and replaces it with another unit having different arrangements of teeth between the various gears and, therefore, providing a different differential feeding motion. When the feed gearing units l are to be interchanged, the re moval of the cover plate 55 permits the nut halves 84 to spring apart and disengage themselves from the threaded portion 49 of the screw shaft I2. The spring 6I within the portion 58 of the cover plate 55 prevents the accidental dropping of the screw shaft I2 by exerting a sufcient frictional drag upon the latter to do so.

What I claim is:

1. A precision boring machine comprising a supporting structure having a work-engaging portion adapted to rest against the work, a rotatable screw shaft journaled in said structure and having a boring tool holder thereon, a nut device rotatably mounted cn said structure and having a threaded nut device including a plurality of transversely-separated threaded components selectively movable into and out of threaded engagement with said screw shaft, feeding mechanism operably connected to said nut device and adapted vto rotate said nut device relatively to said screw shaft whereby to impart longitudinal feeding motion to said tool-holder during rotation thereof, said nut components having bevelled surfaces thereon, and a cover member having a tapered abutment surface engageable with said beveled surfaces to urge said components into engagement with said screw shaft.

2. A precision boring machine comprising a supporting structure having a work-engaging portion adapted te rest against the work, a rotatable screw shaft journaled in said structure, and having a boring tool holder thereon, a nut device rotatably mounted on said structure and having a threaded nut device including a plurality of transversely-separated threaded components selectively movable into and out of 8 threaded engagement with said screw shaft, feeding mechanism operably connected to said nut device and adapted to rotate said nut device relatively to said screw shaft whereby to impart longitudinal feeding motion to said tool-holder during rotation thereof, said components having bevelled surfaces thereon, a cover member having a tapered abutment surface engageable with said bevelled surfaces to urge said components into engagement with said screw shaft, said cover member having an annular recess therein-adjacent said shaft, and an annular resilient friction element seated in said recess and yieldingly and frictionally engaging said screw shaft.

3. A precision boring machine comprising a supporting structure having a substantially cylindrical precision work-locating surface thereon and a work-engaging portion adapted to rest against the work, a rotatable screw shaft journaled in said structure co-axial with said cylindrical portion and having a boring tool-holder thereon, a nut device rotatably mounted on said structure in threaded engagement with said screw shaft, and feeding mechanism operably connected to said nut device and adapted to rotate said nut device relatively to said screw shaft whereby to impart longitudinal feeding motion to said toolholder during rotation thereof.

4. A precision boring machine comprising a supporting structure having a substantially cylindrical precision work-locating surface thereon and a work-engaging portion adapted to rest against the work, a rotatable screw shaft journaled in said structure co-axial with said cylindrical portion and having a boring tool holder thereon, a nut device rotatably mounted on said structure in threaded engagement with said screw shaft, and feeding mechanism operablyconnected to said nut device and adapted to rotate said nut device relatively to said screw shaft whereby to impart longitudinal feeding motion to said toolholder during rotation thereof, said cylindrical surface being disposed on the side of said structure and said work-engaging portion being disposed on the bottom thereof.

5. A precision boring machine comprising a supporting structure having a work-engaging portion adapted to rest against the work, a rotatable screw shaft journaled in said structure and having a boring tool holder thereon, a nut device including a plurality of transversely-separated threaded components rotatably mounted on said structure and selectively movable into and out of threaded engagement with said screw shaft, a resilient frictional element yieldingly and frictionally engaging said screw shaft at a location spaced apart from said nut device, and feeding mechanism operably connected to said nut device and adapted to rotate said nut device relatively to said screw shaft whereby to impart longitudinal feeding motion to said tool-holder during rotation thereof. I

6. A precision boring machine comprising a supporting structure having a work-engaging portion adapted to rest against the work, a rotatable screw shaft journaled in said structure and having a boring tool holder thereon, a nut device including a plurality of transversely-separated threaded components rotatably mounted on said structure and movable axially relatively to said screw shaft and also transversely into and out of threaded engagement with said screw shaft, a stationary wedging member, a follower portion on said nut device responsive .to the axial motion of Said nut device for engaging said stationary wedging member and moving said nut components into threaded engagement with said screw shaft, feeding mechanism operably connected to said nut device and adapted to rotate said nut device relatively to said screw shaft whereby to impart longitudinal feedv ing motion to said tool-holder during rotation thereof, and a control device operably engaging said nut device to move said nut device and shift said nut components into engagement with said i,

screw shaft.

7. A precision boring machine comprising a supporting structure having a work-engaging portion adapted to rest against the work, a rotatable screw shaft journaled in said structure and havinga boring tool holder thereon, a nut device ing rotation thereof, said feeding mechanism including a gearing unit drivingly connecting said screw shaft with said nut device, and a control device having cam mechanism operably engaging said gearing unit to shift said gearing unit bodily in an axial direction relatively to said screw shaft, and wedging mechanism responsive to the shifting of said gearing unit to shift said nut components into engagement with said screw shaft. EDWIN V. STATIA, SR.

REFERENCES CITED The following references are of record in the le of this ipatent:

UNITED STATES PATENTS Number Name Date 1,023,722 Cluts et al Apr. 16, 1912 1,862,866 Storm June 14, 1932 2,039,728 Lundell et al May 5, 1936 2,375,448 Talbot et al May 8, 1945 2,392,564 Wrenn Jan. 8, 1946 2,434,104 Esseling Jan. 6, 1948 2,441,716 Mitchell May 18, 1948 

